Hydraulic pump unit



April 1 1950 E. DRSHANSKY, JR 2,504,041

HYDRAULIC PUMP UNIT Filed NOV. 19, 1946 INVENTOR [00s flrs/mus/K BY Q. 0. AW Wale/VH5 Patented Apr. 11, 1950 E id-4,641

UNITED STATES PATENTWOFFICE HYDRAULIC PUMP UNIT:

Elias Orshansky, Jr., Stamford, Conn, as sig nor.

to The Acrotorque Company, Stamford, .Conn;,'j

a. corporation of Connecticut Application November 19, 194

6 Claims. (01. 103-227)";

This invention relates to hydraulic pump units and more particularly to hydraulic pump units of the positive displacement type. In my co-pending application Serial Number 593,417, filed May 12. 19%, now Patent No. 2,471,117, May 3, 1949, I have described a hydraulic pump unit equipped with mechanism for overcoming the energy losses resulting from elasticity of the unit members and compressibility of the liquid medium employed in the unit. As therein set forth. energy losses in a pump unit due to this elasticity of the parts and the fluid medium, can be avoided by proper control of the valve timing so as to delay the time of opening the inlet valve on the suction stroke of the piston, preferably until the cylinder pressure has been reduced substantia ly to the pressure of the inlet manifold, and mechan sm is disclosed in said application for accomplishing this result.

An object of t is invention is to provide a hydraulic pump unit having an improved and simplified valve mechanism constructedand arranged to compensate for losses due to elasticity.

A further object is to provide a hydraulic pump unit of variable capacity having a variable piston stroke and capable of de ivering a varying pressure, with mechanism constructed and arranged to automatically compensate for varying degrees of elasticity resulting from varied operation of the pump, without requiring any adjustment whatsoever of the timing of the valve mechanism.

These and other objects, which will be apparent are accomplished by the invention hereinafter described and illustrated in the accompanying drawing, in which:

Fig. l is a partial sectional view through a pump unit constructed in accordance with one embodiment of this invention;

Fig. 2 is a section of a line 2-2 of Fig. 1.

In mypreviously filed application, there is described a hydraulic pump unit having an inlet valve mechanism'and a valve-timing mechanism so arranged that under conditions of variable stroke and pressure, opening of the inlet valve is delayed on the suction stroke of the. piston until the pressure in the cylinder is reduced to approximately the pressure in the inlet manifold. AS brought out in the said application, and for "the reasons therein set forth, this timing of the or such aunit. It will be apparent that, in order to gain'this result in a variable capacity pump delivering different fluid pressures, the time of Serial N... imam opening the inletvalve with relation to the piston stroke-will vary under varyingoperating ccndttions. The present invention is designed to accomplish the sameresult, but by means of a greatly simplified and improved mechanism.

The illustrated embodiment of this invention is shown inconnection with a variable pump unit which may, for example, form part of a hydraulic transmission, and which includes a driving shaft ll adapted to be coupled to-any source of power such, for example as an internal combustion engine (not shown) The shaft is supported in anti-friction bearings l2, l3 and I4 mounted within a suitable housing. Each anti-friction bearing is supported on a bearing ring IS on the shaft H. A plurality of pump cylinders 16 is radially disposed around the shaft II and each cylinder has a cylinder head I! threaded or otherwise secured in the end of each cylinder bore. Each cylinder is provided with a piston [8 connected by a connecting rod 19 to a slipper 2| on a collar 22 mounted on an anti-friction hearing supported by the eccentric or crank 24; It will be apparent that the details of the crankassembly can be varied in anydesired manner.

In the illustrated unit. mechanism is provided for varying the length of stroke of the piston 18. This comprises a pair of arcuate segmental racks 25 disposed Within the crank eccentric 24 and secured thereto in any suitable manner. The teeth of the racks engage with similar teeth of keys 21 disposed in keyways 28 on opposite sides of the shaft H. The usual variable counterweights 29 are also mounted on the shaft, as shown. In my Patent No. 2,256,324, September 16, 1941, will be found a detailed description of: this mechanism for varying the'piston stroke and the positions or the associated counterweights. a

However, it can be briefly stated thatthe variation in stroke of the'pisto-n I8 is obtained by longitudinal movement of thekeys 21, which changes the eccentricity of the crank 24 and the relative positions of the counterweight 29. The keys 2 8 are connected to a collar 3i slidably supported on the shaft ll within an anti-friction bearing ring 32 connected to a crank arm 33 secured to. a shaft34, which is adapted to be actuated in any desired manner to determine the position of the keys 2 8 and the eccentricity of the crank 24;.

As illustrated, a double-acting valve element for controlling the inlet and exhaust to and from each cylinder I8 is mountedin a valvebore 4! in which a valve sleeve or liner 42 is located, the end of the valve bore being closed by ahead 43. A spool type valve 44 slidably mounted within the sleeve 42 has extensions 45 pinned to slipper elements 46, which are retained in engagement with a fixed valve operating eccentric 41 on the shaft I I. The valve sleeve 42 has ports 48 communicating with an inlet or low pressure manifold 49 formed in the valve casing. Ports 5| in the sleeve communicate with a high pressure exhaust manifold 52 and ports 53 communicate with a, passage 54 leading to the cylinder port 55. The low preswith a check valve 62 in a valve cage 63 having slotted sides 64, the check valve 62 being biased toward its seat by a spring 65 engaging the ball valve at one end and a closure plug 66 for the valve cage bore at the other end. A passage 61 formed by a bore, the outer end of which is closed by a plug 68, connects the check valve bore 6| gvth the passage 54 leading to the cylinder port The reciprocation of the valve member 44 is so timed by the fixed eccentric 4'! with relation to the reciprocations of the piston [8 to correct for maximum elasticity of the unit, timing the valve 44 so as to open the cylinder inlet 55 to the low pressure manifold 49 after about 60 travel of the piston crank from top dead center. In the illus- "trated pump design, under conditions of maximum elasticity, when the piston is at top dead center the clearance space is filled with fluid at such high pressure that the downward or suction stroke of the piston reduces the cylinder pressure to that of the inlet manifold only after the piston crank has traveled about 60, although, 'of course, this will vary with pumps of different design and with the same pump at different strokes or pressures. At this point, the cylinder pressure is reduced to substantially that of the low pressure manifold and the valve then opens the cylinder to the inlet or low pressure manifold, the eccentric 41 being timed to close the inlet valve when the piston reaches bottom dead center. Under these conditions the check valve 62 remains inoperative.

However, under conditions of less than maximum elasticity, when the cylinder pressure during the suction stroke'is substantially less than that under the above described maximum conditions, it will be apparent that the cylinder pressure will be reduced to less than the inlet manifold pressure at an earlier point in the suction stroke of the piston, or, in other words, before the piston crank has traveled 60. Under these conditions, inasmuch as the valve 44 opens the cylin- 'der to inlet only after a 60 piston crank travel, it will be apparentthat cavitation will occur unless some correction is afforded. This is accom- 'vance the time of opening of the inlet valve to the cylinder when the pressure differential resulting from conditions of less than maximum elasticity requires it. Of course, during the latter part of the suction stroke viz., after 60 crank movement beyond upper dead center, the inlet valve 44 operates to connect the cylinder to the inlet passage 49 in the usual way and the inlet passage is then maintained open until the piston reaches bottom dead center. At that point the valve 44 is moved to close the inlet and connect the cylinder passage 54 with the high pressure exhaust manifold 52.

It will be apparent that the invention can be variously modified and adapted within the scope of the appended claims.

I claim:

1. The combination in a hydraulic pump unit having a cylinder and piston, of means for reciprocating said piston, inlet and exhaust manifolds, inlet valve mechanism, timing means for maintaining said inlet valve closed during the suction stroke of said piston until the cylinder pressure approximates the inlet manifold pressure, and auxiliary inlet valve means actuated by a reduction in cylinder pressure to less than inlet manifold pressure.

2. The combination in a hydraulic pump unit having a cylinder and piston, of means for reciprocating said piston, inlet and exhaust manifolds, a main inlet valve means for compensating for a predetermined maximum characteristic of an operating condition comprising timing means for maintaining said inlet valve closed during the suction stroke of said piston until the cylinder pressure approximates the inlet manifold pressure, means for compensating for a. less than maximum characteristic of said operating condition comprising auxiliary inlet means actuated by a reduction in cylinder pressure to less than inlet manifold pressure for connecting said inlet manifold to said cylinder in advance of the opening of said main inlet valve.

3. The combination in a hydraulic pump unit having a cylinder and piston, of means for reciprocatin said piston, an inlet manifold, an inlet valve mechanism including a mechanically actuated valve member, and an auxiliary valve member responsive to a determinate pressure differential between said cylinder and said inlet manifold for connecting said manifold and cylinder when the cylinder pressure drops below the pressure in the inlet manifold.

4. The combination in a hydraulic pump unit having a cylinder and piston, of means for reciprocating said piston, an inlet-manifold, an inlet valve mechanism including a mechanically actuated main valve, a by-pass connecting said inlet manifold and said cylinder independently of said main valve and means actuated by a determinate pressure differential between said cylinder and inlet manifold for opening said by-pass.

5. The combination in a hydraulic pump unit having a cylinder and piston, of means for reciprocating said piston, an inlet manifold, an inlet valve mechanism including a mechanically actuated main valve, a by-pass connecting said inlet manifold and said cylinder independently of said main valve, and a check valve actuated by a determinate pressure differential between said cylinder and inlet manifold for opening said bypass.

6. The combination in a hydraulic pump unit having a cylinder and piston and piston reciprocating crank, of an inlet manifold, an inlet valve, means for compensating for conditions-of maximum elasticity in said unit comprising means for opening said inlet valve only after the pis- REFERENCES CITED ton Crank has travelled from top dead center The following references are of record in the through a predetermined degree of rotation and fi e 0 1this Patent! for closing said inlet valve at bottom dead center 5 UNITED STATES PATENTS of piston travel, and an auxiliary inlet valve mechanism adapted to open in response to a cyl- Number Name Date inder pressure less than inlet manifold pressure 2,043,524 SVenSOn July 21, 1936 for connecting said manifold to said cylinder, 3 1 Roedel p 8, 1 41 whereby to deliver fluid to said cylinder under 10 2,252,939 MCCOY Aug. 19, 41 predetermined pressure conditions prior to open- 2,256,324 3 '1 p 1941 ing said main inlet valve. 2,328,531 Qulnn S p 7, 943

ELIAS ORSHANSKY J ,958 Celio May 16, 1944 2,471,117 Orshansky, Jr. May 3, 1949 

